CN114250402A

CN114250402A - Manufacturing method of low-carbon nitrogen-containing austenitic stainless steel bar

Info

Publication number: CN114250402A
Application number: CN202111541505.5A
Authority: CN
Inventors: 董晓亮; 张秀丽; 周立新; 雷应华; 王显华; 许广鹏; 徐朋; 孙国洋; 李造宇; 张军; 阮栋
Original assignee: Daye Special Steel Co Ltd
Current assignee: Daye Special Steel Co Ltd
Priority date: 2021-12-16
Filing date: 2021-12-16
Publication date: 2022-03-29
Anticipated expiration: 2041-12-16
Also published as: US20240035110A1; JP2024506434A; JP7471520B2; EP4245880A1; WO2023098919A1; CN114250402B; EP4245880A4; US12024754B2

Abstract

The invention discloses a method for manufacturing a low-carbon nitrogen-containing austenitic stainless steel bar, which sequentially comprises the following steps of: smelting, electroslag remelting and forging; in the electroslag remelting process, the steel ingot obtained in the smelting process is used as an electrode bar of an electroslag furnace, and is remelted and crystallized by specific slag; in the forging procedure, the crystallized steel ingot is forged into a material in a specific forging mode; the specific slag comprises CaF according to the weight percentage₂(65％～70％)、Al₂O₃15-20 percent of CaO, 5-10 percent of CaO and 2-5 percent of MgO; specific forging modes include upsetting and radial forging, wherein upsetting comprises the following steps: the pass deformation is less than 35%, the pass reduction is 50-80 mm, the pass heating temperature is 1130-1150 ℃, and the pass deformation mode is ellipse-circle. By adopting the method, the low-carbon high-strength nitrogen-containing austenitic stainless steel with uniformly distributed chemical components and tissues, high purity and high strength can be obtained.

Description

Manufacturing method of low-carbon nitrogen-containing austenitic stainless steel bar

Technical Field

The invention relates to a method for manufacturing a metal material, in particular to a method for manufacturing a low-carbon high-strength nitrogen-containing austenitic stainless steel bar.

Background

With the rapid development of the current industrialization, the requirements on metal materials are higher and higher, especially in some special environments, such as nuclear power, boilers, military industry and other fields, metal materials which need corrosion resistance, high and low temperature resistance and high strength are often involved, and in the current common steel, only austenitic stainless steel can meet the use requirements, but the austenitic stainless steel has more strict requirements on components and performance indexes.

The current international and domestic standard for the implementation of this type of austenitic stainless steel is RCCM M3306 compiled by the french association for the mechanical equipment design and construction rules of pressurized water reactor nuclear islands, which requires C in the steel: less than or equal to 0.035%, Si: less than or equal to 1.00 percent, Mn: less than or equal to 2.00 percent, S: less than or equal to 0.015 percent, P: less than or equal to 0.030 percent, Cr: 18.50-20.00%, Ni: 9.00-10.00%, Cu: less than or equal to 1.00 percent, Co: less than or equal to 0.06 percent, N: less than or equal to 0.080 percent, B: less than or equal to 0.0018 percent, Nb + Ta: less than or equal to 0.15 percent; in order to ensure the corrosion resistance of the material, the content of carbon and nitrogen elements is limited in the standard: c: less than or equal to 0.035%, N: less than or equal to 0.08 percent; at the same time, the standard requires that the properties for this type of austenitic stainless steel are: the tensile strength at the high temperature of 350 ℃ is more than or equal to 394MPa, the yield strength at the high temperature of 350 ℃ is more than or equal to 125MPa, the tensile strength at the room temperature is more than or equal to 520MPa, and the yield strength at the room temperature is more than or equal to 210 MPa.

However, for low-carbon high-strength nitrogen-containing austenitic stainless steel, the main strengthening elements for improving the strength thereof are carbon and nitrogen elements, and when the contents of the carbon and nitrogen elements are high, the strength of the steel is high, and vice versa. However, when the contents of carbon and nitrogen elements are high, the corrosion resistance of the steel is lowered. In the national standard GB/T1220-2007, the requirement of nitrogen element in the similar low-carbon high-strength nitrogen-containing austenitic stainless steel material is 0.10-0.16%, so that the similar stainless steel can easily realize the high strength of the similar steel in the RCCM M3306 standard, but the corrosion resistance required by the standard is difficult to meet due to the high nitrogen content.

However, the content of nitrogen element in the national standard GB/T1220-2007 is reduced, and the steel can hardly reach the high strength of the steel of the same type in the RCCM M3306 standard. Therefore, compared with the chemical composition requirement of the steel in the RCCM 3306 standard, the production difficulty of the low-carbon high-strength nitrogen-containing austenitic stainless steel is increased.

At present, domestic enterprises often have the situation that the strength of the produced austenitic stainless steel does not meet the standard requirement in the production process, and the yield is low in the production process, so that the steel still needs to be imported from France.

Therefore, a manufacturing method capable of producing a low-carbon high-strength nitrogen-containing austenitic stainless steel with more stable performance is required.

Disclosure of Invention

The invention aims to overcome the problems in the prior art and provide a method for manufacturing a low-carbon nitrogen-containing austenitic stainless steel bar, and the mechanical property of the stainless steel bar manufactured by the method meets the requirement of the RCCM 3306 standard on the mechanical property of an austenitic stainless steel bar, so that the technical barrier is broken through, the autonomous production of the low-carbon high-strength nitrogen-containing austenitic stainless steel bar is realized, and the dependence on the imported stainless steel bar from abroad is avoided.

The inventor of the invention finds that after steel is controlled within the range of specific composition components, a steel ingot is used as an electrode bar for electroslag remelting to be remelted and crystallized, the remelting process is carried out by specific slag, the uniform distribution of chemical components in the steel and the higher purity of the steel can be better controlled, and then the steel ingot is forged into a material by a specific forging mode, so that the steel with uniform distribution of chemical components and tissues, high purity and qualified strength is obtained. Therefore, the invention provides a manufacturing method of the low-carbon high-strength nitrogen-containing austenitic stainless steel bar.

In order to achieve the purpose, the invention adopts the following technical scheme.

A manufacturing method of a low-carbon nitrogen-containing austenitic stainless steel bar sequentially comprises the following steps: smelting, electroslag remelting and forging; in the electroslag remelting process, the steel ingot obtained in the smelting process is used as an electrode bar of an electroslag furnace, and remelting and crystallization are carried out by using specific slag; in the forging procedure, the crystallized steel ingot is forged into a material in a specific forging mode;

the specific slag includes CaF₂、Al₂O₃CaO and MgO, in weight percent, the CaF₂、Al₂O₃CaO and MgO are sequentially (65-70%), (15-20%), (5-10%), (2-5%);

the specific forging modes comprise upsetting and radial forging, wherein the upsetting comprises the following steps: the pass deformation is less than 35% (e.g. 28%, 30%, 32%, 33%, 34%), the pass reduction is 50-80 mm (e.g. 55mm, 60mm, 70mm, 75mm), the pass heating temperature is 1130-1150 ℃ (e.g. 1135 ℃, 1140 ℃, 1145 ℃), and the pass deformation mode is as follows: ellipse-circle. The pass heating temperature refers to the temperature of the furnace returning and heating after the deformation of each pass is finished.

In the invention, the upsetting and the drawing comprise upsetting and drawing, and the steel ingot generally becomes a circle after an ellipse is gradually reduced when a steel ingot is forged and drawn. The rolling reduction is the single rolling height of the press, and the deformation is the change of the front and back areas of the steel.

In the above manufacturing method, as a preferred embodiment, the CaF is preferably contained in a weight percentage₂、Al₂O₃CaO and MgO are sequentially (65-68%), (18-20%), (5-10%), (3-5%), and more preferably CaF₂、Al₂O₃CaO and MgO are 65%, 20%, 10% and 5% in sequence.

In the conventional stainless steel forging process, the pass deformation is generally selected to be 40-60% in order to improve the production efficiency of steel; the heating temperature of each pass is generally 1160-1180 ℃, and the deformation mode of each pass is square-ellipse-circle.

Compared with the conventional stainless steel forging process, the method has the advantages that the pass deformation is less than 35% so as to ensure that the cast structure of the steel ingot is uniformly transformed in the forging process; the pass reduction of 50-80 mm is adopted to ensure uniform deformation of the steel ingot in the forging process and avoid local tissue disorder caused by overlarge reduction; the pass heating temperature is 1130-1150 ℃ (for example, 1135 ℃, 1140 ℃ and 1145 ℃), so as to ensure that the material obtains fine and dispersed tissues; in addition, the invention adopts an ellipse-circle pass deformation mode, and aims to avoid the square edges and corners of the steel, which leads to abnormal steel structure caused by too fast temperature reduction of the edges and corners.

In the above manufacturing method, as a preferred embodiment, the steelmaking raw material is formulated in such a manner that the ingot obtained after the smelting or the finally obtained stainless steel rod has a specific composition, and the specific composition includes, in terms of weight percent: c: 0.020 to 0.030%, Si: 0.3-0.6%, Mn: 1.3-1.8%, S: less than or equal to 0.002%, P: less than or equal to 0.015 percent, Cr: 19.20 to 19.70%, Ni: 9.20-9.80%, Cu: less than or equal to 1.00 percent, Co: less than or equal to 0.06 percent, N: 0.065-0.075%, B: less than or equal to 0.0018 percent, Nb + Ta: less than or equal to 0.15 percent.

Preferably, the specific components comprise, by weight: c: 0.025%, Si: 0.5%, Mn: 1.45%, S: less than or equal to 0.002%, P: less than or equal to 0.015 percent, Cr: 19.5%, Ni: 9.7%, Cu: less than or equal to 1.00 percent, Co: less than or equal to 0.06 percent, N: 0.07%, B: less than or equal to 0.0018 percent, Nb + Ta: less than or equal to 0.15 percent.

In the invention, on the basis of the C content of 0.020-0.030%, the Cr, Ni and N contents are reasonably designed to ensure that the elements can form more carbides, intermetallic compounds and precipitated phases in the steel, and the strength of the steel can be effectively improved in the steel.

In the above manufacturing method, as a preferred embodiment, the steelmaking raw material includes low-carbon ferrochrome, metallic nickel, electrolytic manganese, ferrosilicon, ferrochrome nitride, and scrap steel. In the present invention, the low-carbon ferrochrome, metallic nickel, electrolytic manganese, ferrosilicon, ferrochrome nitride, scrap steel, etc. may be various metals conventionally used in the art for refining 304-series steel.

In the above manufacturing method, as a preferred embodiment, the melting step includes a melting treatment, a refining treatment, a vacuum degassing treatment, and a cast molding in this order.

In the above manufacturing method, as a preferred embodiment, before the electroslag remelting step, the steel ingot obtained in the melting step is subjected to a cutting treatment for cutting off a portion of the feeding defect and a surface polishing treatment for polishing the surface of the steel ingot, and then the steel ingot is used as an electrode rod for electroslag remelting; the surface finishing treatment is used to obtain electrode rods with good surface quality. After the cutting treatment and the surface polishing treatment, the chemical components of the remelted steel ingot can be ensured to be uniform and the surface quality is good, so that the steel with better surface quality, high purity, uniform structure and high strength can be obtained.

In the above manufacturing method, as a preferred embodiment, in the electroslag remelting step, the current for electroslag remelting is 11 to 13KA (e.g., 11.5KA, 12.0KA, 12.5 KA).

In the invention, in the electroslag remelting process, the female electrode can be rapidly melted due to overlarge current, so that a metal molten pool becomes deep, and the core of the steel ingot obtained after crystallization has a serious segregation structure and poor purity. The female electrode is melted slowly due to the over-small current, so that a metal molten pool becomes shallow, and the edge of a steel ingot obtained after crystallization has a serious segregation structure and poor purity.

In the invention, in the electroslag remelting process, the raw materials comprise (65-70%), 15-20%), 5-10% and 2-5%, preferably 65%, 20%, 10% and 5% of CaF in sequence by weight percentage₂、Al₂O₃And the mixed slag (specific slag) of CaO and MgO is remelted and crystallized, so that the purity of the steel can be effectively improved. Here, CaF₂The melting point, viscosity and surface tension of slag can be reduced, the fluidity of slag is improved, and nonmetallic inclusions in steel can be effectively eliminated; al (Al)₂O₃The conductivity of the molten slag can be reduced, the effects of saving energy and reducing consumption are achieved, but the viscosity of the molten slag can be improved by adding too much; CaO can improve the alkalinity of the slag, and the effective desulfurization capability ensures that the molten steel is purer; MgO can form a slag film on the surface of the slag, can prevent the secondary oxidation of the molten steel outwards, and can reduce the heat loss inwards, but the viscosity of the slag is improved by adding too much MgO. Therefore, the four-element slag system consisting of the four substances can obtain steel with higher purity and reduce energy consumption.

In the invention, if the selected slag and the current are not suitable, slag rolling and wrapping can occurLow purity of slag and molten steel, serious steel segregation, poor surface quality of steel ingots and the like. The invention adopts the CaF content according to the mass ratio₂、Al₂O₃The CaO and the MgO are sequentially (65-70%), (15-20%), (5-10%), (2-5%), preferably, the specific slag charge proportion of 65%, 20%, 10% and 5% and the remelting current of 11-13 KA and preferably 11KA, so that the electrode bar can be ensured to be stably molten, and a steel ingot with high purity, uniform structure and components and good surface can be obtained.

In the above manufacturing method, as a preferred embodiment, in order to obtain steel having a high surface quality, 1 to 10 wt%, preferably 1 to 8 wt% (for example, 2 wt%, 3 wt%, 5 wt%, 6 wt%, 7 wt%) of the electrode rod is used for feeding the steel ingot after crystallization in the electroslag remelting step. That is, when molten steel is dropped into a mold for crystallization, a shrinkage cavity will exist on the surface of a steel ingot due to the action of the surface tension of the molten steel, and in order to avoid the problem that the quality of the processing plasticity is affected due to the poor surface quality of steel obtained after forging caused by the large shrinkage cavity formed in the steel ingot, it is preferable that 1 to 10 wt%, more preferably 1 to 8 wt%, of the electrode rod be used to fill up the shrinkage cavity on the surface of the steel ingot formed after crystallization at the later stage of crystallization.

In the above manufacturing method, as a preferred embodiment, the steel ingot obtained by electroslag remelting is demolded and cooled to room temperature to obtain a low-carbon nitrogen-containing austenitic stainless steel blank.

The low-carbon nitrogen-containing austenitic stainless steel blank prepared by the technical scheme of the invention has the advantages of uniform distribution of chemical components, high purity and no segregation defect, and can be used for manufacturing a low-carbon high-strength nitrogen-containing austenitic stainless steel bar, but the manufacturing method of the low-carbon high-strength nitrogen-containing austenitic stainless steel bar needs to meet special requirements.

In the above-described manufacturing method, as a preferred embodiment, in the forging step, the low-carbon nitrogen-containing austenitic stainless steel blank obtained by electroslag remelting is subjected to soaking treatment before upsetting, and the soaking treatment includes raising the temperature to 1130 to 1150 ℃ (e.g., 1135 ℃, 1140 ℃, 1145 ℃) at a heating rate of 1 to 10 ℃/min (e.g., 2 ℃/min, 3 ℃/min, 5 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min), and then maintaining the temperature for 3 to 5 hours (e.g., 3.5 hours, 4.0 hours, 4.5 hours).

In the above manufacturing method, as a preferred embodiment, the upsetting condition in the forging step includes: upsetting and drawing by the specific forging method, wherein the forging temperature is more than or equal to 1000 ℃ (such as 1050 ℃, 1100 ℃, 1110 ℃ and 1120 ℃), the finish forging temperature is more than or equal to 800 ℃ (such as 850 ℃, 900 ℃, 950 ℃ and 1000 ℃), and the upsetting and drawing frequency is 1-3 times (such as 2 times), preferably 2-3 times; the time of each upsetting is 5-20 min (for example, 8min, 10min, 12min, 15min, 17min, 19 min).

In the above manufacturing method, as a preferred embodiment, the upsetting condition in the forging step includes: the upsetting is performed by the specific forging method, the forging temperature is 1050 to 1100 ℃ (e.g., 1060 ℃, 1070 ℃, 1080 ℃ and 1090 ℃) and the finish forging temperature is 800 to 900 ℃ (e.g., 820 ℃, 850 ℃, 870 ℃ and 890 ℃), and the time for each upsetting is preferably 5 to 15min (e.g., 7min, 9min, 10min, 12min and 14 min).

In the above manufacturing method, as a preferred embodiment, the specific forging method in the upsetting in the forging step includes: the pass deformation is 30-32% (e.g., 30.5%, 31%, 31.5%), the pass reduction is 65-75 mm (e.g., 67mm, 70mm, 72mm, 74mm), the pass heating temperature is 1130-1150 ℃ (e.g., 1135 ℃, 1140 ℃, 1145 ℃), and the pass deformation mode is as follows: ellipse-circle.

In the above manufacturing method, as a preferred embodiment, the specific forging method in the upsetting in the forging step includes: the pass deformation is 31 percent, the pass reduction is 70mm, the pass heating temperature is 1140 ℃, and the pass deformation mode is as follows: ellipse-circle.

In the above manufacturing method, as a preferred embodiment, in the upsetting in the forging step, double upsetting and double drawing (i.e., double upsetting) is performed in a 4500t press, and the second upsetting deformation is larger than the first deformation, so that the problem of coarse structure caused by the return process after the first upsetting is completed can be solved, and the obtained steel product can have a better grain size.

In the above manufacturing method, as a preferred embodiment, in the upsetting in the forging step, each time the upsetting (upsetting and elongating) is completed, the forging is performed by returning to the furnace to perform the reheating so as to reach the forging temperature required for the next upsetting, and preferably, the conditions of the returning to the furnace and the reheating (i.e., the pass heating) after each upsetting are: the temperature is 1130-1150 deg.C (e.g., 1135 deg.C, 1140 deg.C, 1145 deg.C), and the time is 90-120 min (e.g., 95min, 100min, 110min, 115 min).

After the final upsetting and drawing, the steel sheet can be heated again by the above-mentioned reheating and heating conditions to prepare for the subsequent radial forging.

In the above manufacturing method, as a preferred embodiment, the forging step further includes diameter forging after the end of the upsetting; the radial forging conditions include: the forging temperature is 1000 to 1140 ℃ (for example, 1020 ℃, 1040 ℃, 1050 ℃, 1070 ℃, 1090 ℃, 1115 ℃, 1125 ℃, 1130 ℃, 1135 ℃), and the finish forging temperature is 800 to 900 ℃ (for example, 820 ℃, 850 ℃, 870 ℃, 890 ℃) for 5 to 20min (for example, 8min, 10min, 12min, 15min, 17min, 19 min).

Still preferably, the conditions of the radial forging include: the forging temperature is 1000 to 1100 ℃ (for example, 1005 ℃, 1010 ℃, 1020 ℃, 1040 ℃, 1050 ℃, 1070 ℃, 1080 ℃ and 1090 ℃), and the finish forging temperature is 800 to 900 ℃ (for example, 820 ℃, 850 ℃, 870 ℃, 890 ℃), and the time is 10 to 20min (for example, 12min, 15min, 17min, and 18 min).

More preferably, the radial forging is carried out on a 1600t radial forging machine, one-time forging forming is carried out, and the radial forged steel is cooled in air, so that the low-carbon nitrogen-containing austenitic stainless steel rod is obtained.

By adopting the method, the low-carbon nitrogen-containing austenitic stainless steel bar with the diameter of more than 200mm can be prepared.

In the above manufacturing method, as a preferred embodiment, the obtained low-carbon nitrogen-containing austenitic stainless steel bar has a tensile strength at high temperature at 350 ℃ of not less than 410MPa, a yield strength at high temperature at 350 ℃ of not less than 140MPa, a tensile strength at room temperature of not less than 560MPa, a yield strength at room temperature of not less than 260MPa, uniform chemical components and high-power structure, and high purity of steel.

In the invention, the technical characteristics can be freely combined to form a new technical scheme under the condition of not conflicting with each other.

Compared with the prior art, the invention has the following beneficial technical effects:

1. by adopting the technical scheme of the invention, the uniform distribution of chemical components in the steel and the higher purity of the steel can be better controlled.

2. By adopting the technical scheme of the invention, the low-carbon high-strength nitrogen-containing austenitic stainless steel with uniformly distributed chemical components and tissues, high purity and high strength can be obtained.

Detailed Description

The following describes the technical solutions of the embodiments of the present invention in detail with reference to the examples of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without any creative efforts shall fall within the protection scope of the present invention.

The invention provides a method for manufacturing a low-carbon high-strength nitrogen-containing austenitic stainless steel bar, which comprises the following steps of: smelting, electroslag remelting and forging; wherein,

a smelting process: adding a steelmaking raw material into an electric arc furnace, an external refining furnace and a vacuum oxygen-blowing decarburization furnace for smelting, wherein the smelting sequentially comprises melting treatment, refining treatment, first sample preparation treatment, oxygen-blowing decarburization treatment, degassing treatment, nitrogen-blowing treatment, second sample preparation treatment and casting molding; the steelmaking raw materials are proportioned in a mode that the finally obtained steel ingot has specific components, and the specific components comprise the following components in percentage by weight: c: 0.020 to 0.030%, Si: 0.3-0.6%, Mn: 1.3-1.8%, S: less than or equal to 0.002%, P: less than or equal to 0.015 percent, Cr: 19.20 to 19.70%, Ni: 9.20-9.80%, Cu: less than or equal to 1.00 percent, Co: less than or equal to 0.06 percent, N: 0.065-0.075%, B: less than or equal to 0.0018 percent, Nb + Ta: less than or equal to 0.15 percent;

an electroslag remelting process: firstly, cutting off and polishing the steel ingot obtained in the smelting process, then remelting and crystallizing the steel ingot by using specific slag as an electrode bar for electroslag remelting, and cooling the crystallized steel ingot; the specific slag includes CaF₂、Al₂O₃CaO and MgO, in weight percent, the CaF₂、Al₂O₃CaO and MgO are sequentially (65-70%), (15-20%), (8-10%), (2-5%), and the sum of the proportions of the final proportioning is ensured to be 100%;

forging: cooling the crystallized steel ingot; in the forging procedure, the crystallized steel ingot is forged into a material in a specific forging mode; said specific forging regime comprises upsetting and diameter forging, said upsetting comprising upsetting and elongating wherein said upsetting comprises: the pass deformation is less than 35% (e.g. 28%, 30%, 32%, 33%, 34%), the pass reduction is 50-80 mm (e.g. 55mm, 60mm, 70mm, 75mm), the pass heating temperature is 1130-1150 ℃ (e.g. 1135 ℃, 1140 ℃, 1145 ℃), and the pass deformation mode is as follows: ellipse-circle. The pass heating temperature refers to the temperature of the furnace returning and heating after the deformation of each pass is finished.

In the present invention, the melting process may employ a conventional technical scheme in the art.

According to the present invention, as a preferred embodiment, the steelmaking raw material includes low carbon ferrochrome, metallic nickel, electrolytic manganese, ferrosilicon, ferrochrome nitride, scrap steel, etc., and the low carbon ferrochrome, metallic nickel, electrolytic manganese, ferrosilicon, ferrochrome nitride, scrap steel, etc., may be various metals conventionally used in the art for refining 304 series steel, for example, the metallic nickel is 1# Ni, etc.

According to the invention, as a preferred embodiment, the specific components comprise, in weight percent: c: 0.025%, Si: 0.5%, Mn: 1.45%, S: less than or equal to 0.002%, P: less than or equal to 0.015 percent, Cr: 19.5%, Ni: 9.7%, Cu: less than or equal to 1.00 percent, Co: less than or equal to 0.06 percent, N: 0.07%, B: less than or equal to 0.0018 percent, Nb + Ta: less than or equal to 0.15 percent.

Although the steel-making raw material can be prepared according to the above composition, in order to obtain a better steel ingot, it is preferable that a part of the low-carbon ferrochrome and the ferrochrome nitride in the steel-making raw material is reserved in the smelting treatment process as the feed for the second sample preparation treatment.

According to a preferred embodiment of the present invention, the melting treatment is a process in which a steelmaking material is charged into an electric arc furnace such as a vacuum arc furnace, and then the steelmaking material is melted and mixed by electrode heating, oxygen blowing, and slag addition. Preferably, the tapping conditions of the melting process comprise: c is less than or equal to 0.60 percent, and T is more than or equal to 1630 ℃.

According to the invention, as a preferred embodiment, the refining treatment is that molten steel melted by an electric furnace is poured into an external refining furnace, the molten steel in the electric arc furnace is subjected to reduction treatment through electrode heating and slag adding treatment, preferably, 5-10 kg/t of Si-C powder is added, deoxidation is carried out, and electric slag burning is carried out for more than 10 minutes. Adjusting the slag to be proper (namely adjusting the slag to be white), sampling and fully analyzing, and returning a sample and adjusting the components. Preferably, the tapping condition T is more than or equal to 1650 ℃, and the tapping components are as follows: less than or equal to 0.80 percent of C, less than or equal to 0.30 percent of Si and less than or equal to 0.015 percent of S.

According to the invention, as a preferred embodiment, the vacuum oxygen decarburization treatment, the degassing treatment and the nitrogen blowing treatment are carried out in a vacuum oxygen decarburization furnace, which means that the molten steel of a refining furnace outside the furnace is subjected to the vacuum oxygen decarburization treatment to remove the carbon content of the steel, then slag charge and a deoxidizer are added under vacuum to carry out the vacuum degassing treatment to remove oxides left in the steel after the oxygen decarburization, the nitrogen blowing treatment at the bottom of the furnace is carried out after the deoxidation is finished to increase the nitrogen content in the steel, and finally the reserved low-carbon ferrochrome and the reserved nitrided ferrochrome are added according to chemical components; preferably, the molten steel is completely discharged outside the furnace before entering the vacuum oxygen blowing decarburization furnace, and the slag charge proportion of the vacuum degassing treatment is as follows: 400kg of lime, 50-100 kg of fluorite and 200-300 kg of pre-dissolved aluminum-calcium composite slag per furnace; the deoxidizer is Al particles, Ca-Si or Fe-Si; preferably, 1-3 kg/t of deoxidizer Al particles and 5-8 kg/t of Ca-Si or Fe-Si are added along with slag charge; the vacuum degree of the vacuum degassing treatment is less than or equal to 100Pa, and the holding time is more than or equal to 10 min.

According to the invention, as a preferred embodiment, the casting molding means that molten steel with qualified chemical composition obtained by vacuum degassing treatment is cast into an electrode, preferably, argon is blown at the bottom of a furnace for 20 minutes before casting, and the casting is carried out under the protection of argon, wherein the casting temperature is 1530-1550 ℃.

According to the present invention, as a preferred embodiment, a steel ingot having the composition of the present invention, particularly a steel ingot produced by the above-described production method, is remelted and crystallized as an electrode rod for electroslag remelting.

In the present invention, in order to obtain a steel material having a better surface quality, a high purity, a uniform structure, and a high strength, it is necessary to ensure that the chemical composition of the steel ingot after remelting is uniform and the surface quality is good, and it is preferable that the steel ingot as the electrode rod is first subjected to cutting-off treatment and surface polishing treatment. The cutting process is used for cutting off the defective feeding part; the surface finishing treatment is used to obtain electrode rods with good surface quality.

According to the present invention, as a preferred embodiment, in the electroslag remelting step, the ingot obtained by casting molding is used as an electrode rod of an electroslag furnace, the electrode rod melts into molten steel in slag under the condition of energization, and the molten steel is dripped into a crystallizer through the slag to be crystallized; preferably, the specific slag charge ratio is as follows according to the weight percentage: CaF₂：65％、Al₂O₃: 20%, CaO: 10%, MgO: 5 percent, and the current of electroslag remelting is 11 KA.

According to the present invention, in order to obtain a steel with high surface quality, it is preferable that 1 to 10 wt% (more preferably 1 to 8 wt%) of the electrode rod is used for feeding the steel ingot after crystallization, that is, when molten steel is dropped into a mold for crystallization, a shrinkage cavity will exist on the surface of the steel ingot due to the surface tension of the molten steel, and in order to avoid the influence of the poor surface quality of the steel obtained after forging caused by the large shrinkage cavity formed in the steel ingot on the quality of the working plasticity thereof, it is preferable that 1 to 10 wt% (more preferably 1 to 8 wt%) of the electrode rod is used for feeding the shrinkage cavity on the surface of the steel ingot formed after crystallization at the latter stage of crystallization.

The low-carbon nitrogen-containing austenitic stainless steel obtained by the manufacturing method has the advantages of uniform chemical component distribution, high purity and no segregation defect, and can be used for manufacturing a low-carbon high-strength nitrogen-containing austenitic stainless steel bar.

In the above manufacturing method, as a preferred embodiment, in the forging step, the specific forging method is upsetting and diameter forging the steel ingot after soaking; the soaking treatment is to cool the steel ingot obtained in the electroslag remelting process and then perform heating treatment, and the soaking treatment comprises the following steps: heating to 1130-1150 ℃ at a heating speed of 1-10 ℃/min, and then preserving heat for 3-5 h; the upsetting includes upsetting and elongating.

In the above manufacturing method, as a preferred embodiment, the upsetting condition in the forging step includes: the forging starting temperature is more than or equal to 1000 ℃, the finish forging temperature is more than or equal to 800 ℃, and the time of each upsetting and drawing is 5-20 min; the pass deformation is 30-32%, the pass reduction is 65-75 mm, the pass heating temperature is 1130-1150 ℃, and the pass deformation mode is as follows: ellipse-circle.

Preferably, the condition of upsetting comprises: the opening forging temperature is 1050-1100 ℃, the final forging temperature is 800-900 ℃, and the time of each upsetting and drawing is 5-15 min; the number of upsetting can be 1-3, preferably 2-3; more preferably, the two upsetting and two drawing are carried out in a 4500t press, and the deformation of the second upsetting and two drawing is larger than that of the first upsetting and two drawing, so that the problem of coarse structures caused by the process of returning after the first upsetting and two drawing can be solved, and the obtained steel can have better grain size.

Wherein, each upsetting (including upsetting and elongation) is finished, the furnace is returned to be re-burnt to reach the forging temperature required by upsetting, and preferably, the conditions of returning to the furnace and re-burning after each upsetting are as follows: the temperature is 1130-1150 ℃, the time is 90-120 min, the returning conditions including the last upsetting and drawing can adopt the returning conditions, the pass deformation is 31%, the pass reduction is 70mm, the pass heating temperature is 1140 ℃, and the pass deformation mode is as follows: ellipse-circle.

In the above manufacturing method, as a preferred embodiment, the forging step is performed after the upsetting, and the open forging temperature of the radial forging is the temperature of the steel after the reheating. Preferably, the conditions of the radial forging include: the open forging temperature is 1120-1140 ℃, the finish forging temperature is 800-900 ℃, and the time is 5-20 min. Still preferably, the conditions of the radial forging include: the start forging temperature is 1000-1100 ℃, the finish forging temperature is 800-900 ℃, and the time is 10-20 min; still preferably, the radial forging is performed on a 1600t radial forging machine, and one-pass forging is performed, and the steel after the radial forging is air-cooled.

The low-carbon high-strength nitrogen-containing austenitic stainless steel prepared by the method can be used for preparing a steel bar with the diameter of more than 200mm, the tensile strength at the high temperature of 350 ℃ of the obtained low-carbon high-strength nitrogen-containing austenitic stainless steel is more than or equal to 410MPa, the yield strength at the high temperature of 350 ℃ is more than or equal to 140MPa, the tensile strength at the room temperature is more than or equal to 560MPa, the yield strength at the room temperature is more than or equal to 260MPa, the chemical components and the high-power structure are uniform, and the purity of the steel is high.

The present invention will be described in detail below by way of examples.

In the examples, the tensile strength Rm, the yield strength rp0.2, the elongation after fracture a, and the reduction of area Z were measured by the methods described in RCCM M1000.

Example 1

The embodiment provides a method for manufacturing a low-carbon high-strength nitrogen-containing austenitic stainless steel bar, which sequentially comprises the following steps of: smelting, electroslag remelting and forging. In particular, the amount of the solvent to be used,

a smelting process:

(1) preparing materials: the method comprises the following steps of mixing low-carbon ferrochrome, metallic nickel, electrolytic manganese, ferrosilicon, ferrochrome nitride and scrap steel, and preparing a steel ingot containing C: 0.026%, Si: 0.54%, Mn: 1.45%, S: less than or equal to 0.002%, P: 0.017%, Cr: 19.7%, Ni: 9.7%, Cu: less than or equal to 1.00 percent, Co: less than or equal to 0.06 percent, N: 0.072%, B: less than or equal to 0.0018 percent, Nb + Ta: batching in a mode of less than or equal to 0.15 percent, wherein 1/3 weight parts of the low-carbon ferrochrome and the nitriding ferrochrome are reserved respectively.

(2) Melting treatment: adding the steel-making raw materials obtained after the material mixing into an electric arc furnace for melting treatment, firstly inserting an electrode into an alloy material for feeding the material, simultaneously inserting an oxygen lance into the furnace bottom for oxygen blowing and fluxing, adding lime into the surface of the steel-making raw materials, and melting and mixing the steel-making raw materials through electrode heating, oxygen blowing and slag adding. When tapping is carried out on the electric furnace: c: 0.56 wt% and the tapping temperature is 1690 ℃.

(3) Refining treatment: pouring molten steel melted by an electric furnace into an external refining furnace, adding 15kg of Si-C powder and 400kg of synthetic slag, electrically burning the slag for 15 minutes, sampling after power failure, fully analyzing, and adjusting the components (namely, the first sample preparation treatment). Tapping condition T: 1670 ℃, discharge component: c: 0.40%, Si: 0.25%, S: 0.005 percent.

(4) Oxygen blowing decarburization treatment, degassing treatment, nitrogen blowing treatment, second sample preparation treatment and casting molding:

pouring molten steel after refining tapping into a vacuum oxygen blowing decarburization furnace for oxygen blowing treatment in vacuum, sampling after oxygen blowing until the carbon content in the steel is 0.005%, then pouring 400kg of lime, 80kg of fluorite and 200kg of synthetic slag into the molten steel, adding 20kg of deoxidizer Al particles and 20kg of Ca-Si along with slag materials for degassing treatment, wherein the vacuum degree is 67Pa, and the holding time is 15 min.

And blowing nitrogen into the molten steel after degassing is finished, then adding the reserved low-carbon ferrochromium and manganese metal, blowing argon into the molten steel for 20min after the metal materials are melted, and then pouring 2.5 tons of electrode molds with the diameter of 410mm under the protection of argon. Blowing argon gas at the bottom of the furnace for 20 minutes before pouring, then pouring under the protection of argon gas, wherein the pouring temperature is as follows: and at 1530-1550 ℃, remaining 400kg of residual casting after casting.

Cutting treatment and surface polishing treatment:

and cutting off the filling part of the steel ingot obtained in the smelting process, and polishing the surface of the steel ingot.

An electroslag remelting process:

remelting the steel ingot with the polished surface as an electrode bar of an electroslag furnace, wherein the weight of slag in the remelting process is 130kg, and the slag proportion is as follows: CaF₂：Al₂O₃: CaO: MgO 65%: 20%: 10%: 5%, the remelting current is 11KA, and the remelting voltage is as follows: 45V, and (5); the molten steel is dropped into a crystallizer with a diameter of 510mm (phi 510mm) for crystallization, and when 360kg of electrode bar remains, the electrode bar is placed in the crystallizerAnd (3) performing feeding treatment on the shrinkage cavity of the steel ingot as a feeding material of the steel ingot in the crystallizer.

And (4) after the smelting is finished, demoulding the steel ingot and cooling to room temperature to obtain the steel ingot with the diameter of 510 mm.

Forging: forging in a specific forging mode, wherein the forging mode comprises soaking treatment and forging, the forging mode comprises upsetting and radial forging, and the specific forging mode comprises the following steps: the pass deformation is 31 percent, the pass reduction is 70mm, the pass heating temperature is 1140 ℃, and the pass deformation mode is ellipse-circle. In particular, the amount of the solvent to be used,

soaking treatment: soaking the air-cooled 2.5-ton (phi 510mm) steel ingot under the soaking conditions: firstly heating the mixture to 1150 ℃ at the heating rate of 2.3 ℃/min, and preserving the heat for 4 h.

Upsetting and drawing (including upsetting and drawing) and diameter forging: the steel ingot after soaking treatment is sent into a 4500t press for upsetting and drawing for the first time for 8min, the finish forging temperature is 850 ℃, the diameter is 530mm, the reduction is 70mm, and the deformation mode is phi 540mm ellipse-phi 535mm ellipse-phi 530mm circle (the ellipse is also called a pierced billet in the production process, namely an irregular circle, and the diameter is the average value of the major diameter and the minor diameter); then the blank is heated in a furnace again at 1140 ℃ for 90min, and is sent into a press of 4500t for second upsetting and drawing for 10min, the final forging temperature is 850 ℃ until the diameter is 510mm, the reduction is 70mm, and the deformation mode is phi 520mm ellipse-phi 515mm ellipse-phi 510mm circle; then the steel is heated in a furnace returning mode at 1140 ℃ for 90min, and is sent into a press of 4500t for first drawing for 15min until the diameter is 420mm, the reduction is 70mm, the deformation is 31 percent, and the deformation mode is phi 430mm ellipse-phi 425mm ellipse-phi 420mm circle; then the steel is heated in a furnace returning mode at 1140 ℃ for 90min, and is sent into a press of 4500t for secondary drawing for 15min until the diameter is 350mm, the reduction is 70mm, the deformation is 31 percent, and the deformation mode is phi 360mm ellipse-phi 355mm ellipse-phi 350mm circle; and then the steel is heated in a furnace for 90min at 1140 ℃, and then is forged for 20min in a 1600 t-diameter forging machine for one fire time, the final forging temperature is 850 ℃, the diameter after forging is 200mm, and then the steel is air-cooled to room temperature to obtain the 00Cr19Ni10N steel bar with the diameter of 200mm, wherein the tensile strength at 350 ℃, the yield strength at 350 ℃, the tensile strength at room temperature and the yield strength at room temperature all meet the requirements of the RCCMM3306 standard, and the steel has uniform chemical components and high-low magnification tissues and high purity of steel, and is concretely shown in tables 1 and 2.

TABLE 1 Properties and Structure of Low-carbon Nitrogen-containing Austenitic stainless Steel rod prepared in example 1

TABLE 2 chemical composition (wt%) of the low carbon nitrogen austenitic stainless steel bar prepared in example 1

C	Si	Mn	P	S	Cr	Ni	N	Nb+Ta	Co	Cu	B
												0.026	0.54	1.45	0.017	0.002	19.7	9.7	0.072	0.008	0.03	0.2	0.0009

Example 2

The embodiment provides a method for manufacturing a low-carbon high-strength nitrogen-containing austenitic stainless steel bar, which sequentially comprises the following steps of: smelting, electroslag remelting and forging. Except that the following technical scheme is adopted in the material preparation step in the smelting process, the technical scheme in the embodiment 1 is adopted in other steps of the smelting process and in the electroslag remelting and forging processes.

A smelting process:

(1) preparing materials: the method comprises the following steps of mixing low-carbon ferrochrome, metallic nickel, electrolytic manganese, ferrosilicon, ferrochrome nitride and scrap steel, and preparing a steel ingot containing C: 0.026%, Si: 0.54%, Mn: 1.45%, S: less than or equal to 0.002%, P: less than or equal to 0.017 percent, Cr: 19.2%, Ni: 9.2%, Cu: less than or equal to 1.00 percent, Co: less than or equal to 0.06 percent, N: 0.072%, B: less than or equal to 0.0018 percent, Nb + Ta: batching in a mode of less than or equal to 0.15 percent, wherein 1/3 weight parts of the low-carbon ferrochrome and the nitriding ferrochrome are reserved respectively.

The above ingredients are adopted for smelting, electroslag remelting and forging, the diameter is 200mm after final forging, then the air cooling is carried out to the room temperature, the 00Cr19Ni10N steel bar with the diameter of 200mm is obtained, the tensile strength at the high temperature of 350 ℃, the yield strength at the high temperature of 350 ℃, the tensile strength at the room temperature and the yield strength at the room temperature can not meet the requirements of the RCCMM3306 standard, and the details are shown in tables 3 and 4.

TABLE 3 Properties and Structure of Low-carbon Nitrogen-containing Austenitic stainless Steel rod prepared in example 2

TABLE 4 chemical composition (wt%) of the low carbon nitrogen austenitic stainless steel bar prepared in example 2

C	Si	Mn	P	S	Cr	Ni	N	Nb+Ta	Co	Cu	B
												0.026	0.54	1.45	0.017	0.002	19.2	9.2	0.072	0.008	0.03	0.2	0.0009

Example 3

The embodiment provides a method for manufacturing a low-carbon high-strength nitrogen-containing austenitic stainless steel bar, which sequentially comprises the following steps of: smelting, electroslag remelting and forging. The smelting and electroslag remelting process adopts the same technical scheme as the embodiment 2, and the forging process adopts the following technical scheme:

forging: forging in a specific forging mode, wherein the forging mode comprises soaking treatment and forging, the forging mode comprises upsetting and radial forging, and the specific forging mode comprises the following steps: the pass deformation is 31 percent, the pass reduction is 65mm, the pass heating temperature is 1140 ℃, and the pass deformation mode is ellipse-circle. The rolling reduction is the single rolling height of the press, and the deformation is the change of the front and back areas of the steel. In particular, the amount of the solvent to be used,

Upsetting and drawing and diameter forging: the steel ingot after soaking treatment is sent into a 4500t press for first upsetting and drawing for 15min, the finish forging temperature is 800 ℃, the diameter is 530mm, the rolling reduction is 65mm, and the deformation mode is phi 540mm ellipse-phi 535mm ellipse-phi 530mm circle; then the blank is heated in a furnace again and heated at 1130 ℃ for 90min, and then the blank is sent into a press of 4500t for second upsetting and drawing for 15min, wherein the final forging temperature is 800 ℃ until the diameter is 510mm, the reduction is 65mm, and the deformation mode is phi 520mm ellipse-phi 515mm ellipse-phi 510mm circle; then the steel is heated in a furnace again at 1130 ℃ for 90min, and then the steel is sent into a press of 4500t for first drawing for 15min until the diameter is 420mm, the rolling reduction is 65mm, the deformation is 31 percent, and the deformation mode is phi 430mm ellipse-phi 425mm ellipse-phi 420mm circle; then the steel is heated in a furnace for 90min at 1130 ℃, and then the steel is sent into a press of 4500t for secondary drawing for 15min until the diameter is 350mm, the rolling reduction is 65mm, the deformation is 31 percent, and the deformation mode is phi 360mm ellipse-phi 355mm ellipse-phi 350mm circle; then the steel bar is heated in a furnace for 90min at 1140 ℃, then is forged for 20min in a forging machine with 1600t diameter for one fire time, the finish forging temperature is 850 ℃, the diameter after forging is 200mm, and then the steel bar is air-cooled to room temperature to obtain the 00Cr19Ni10N steel bar with the diameter of 200 mm.

TABLE 5 Properties and Structure of Low-carbon Nitrogen-containing Austenitic stainless Steel rod prepared in example 3

The 350 ℃ high-temperature tensile strength, the 350 ℃ high-temperature yield strength, the room temperature tensile strength and the room temperature yield strength of the 00Cr19Ni10N steel bar all meet the requirements of the RCCMM3306 standard, the chemical components and the high-power structure are uniform, and the purity of steel is high, which is shown in tables 5 and 6.

TABLE 6 chemical composition (wt%) of the low carbon nitrogen austenitic stainless steel bar prepared in example 3

Comparative example 1

The comparative example provides a manufacturing method for producing a low-carbon high-strength nitrogen-containing austenitic stainless steel bar by adopting a conventional electroslag process, which sequentially comprises the following working procedures: smelting, electroslag remelting and forging. The smelting and forging process adopts the same technical scheme as the smelting and forging process in the embodiment 1, and the electroslag remelting process adopts the following technical scheme:

an electroslag remelting process:

grind the surfaceThe polished steel ingot is used as an electrode bar of an electroslag furnace for remelting, the weight of slag in the remelting process is 130kg, and the slag proportion is as follows: CaF₂：Al₂O₃70%: 30%, the remelting current is 12KA, and the remelting voltage is as follows: 45V, and (5); and (3) dropping the molten steel into a crystallizer with the diameter of 510mm for crystallization, and performing feeding treatment on the shrinkage cavity of the steel ingot by taking the molten steel as a feeding material of the steel ingot in the crystallizer when 360kg of electrode rods are remained.

And (5) demolding the steel ingot after the smelting is finished, and cooling to room temperature.

Then, the steel ingot obtained in the electroslag remelting process is forged to obtain a steel bar with the diameter of 200mm, and then the steel bar is air-cooled to room temperature to obtain a 00Cr19Ni10N steel bar with the diameter of 200mm, wherein the tensile strength at the high temperature of 350 ℃, the yield strength at the high temperature of 350 ℃, the tensile strength at the room temperature and the yield strength at the room temperature all can not meet the requirements of the RCCMM3306 standard, the purity of the steel is low, and the macrostructure is uneven, which is specifically shown in tables 7 and 8.

TABLE 7 Properties and structures of low-carbon nitrogen-containing austenitic stainless steel bars prepared in comparative example 1

TABLE 8 chemical composition (wt%) of the low carbon nitrogen austenitic stainless steel bar prepared in comparative example 1

C	Si	Mn	P	S	Cr	Ni	N	Nb+Ta	Co	Cu	B
												0.026	0.54	1.45	0.017	0.002	19.7	9.6	0.072	0.008	0.03	0.2	0.0009

Comparative example 2

The comparative example provides a manufacturing method of a low-carbon high-strength nitrogen-containing austenitic stainless steel bar produced by adopting a conventional forging process, which sequentially comprises the following working procedures: smelting, electroslag remelting and forging. The smelting and electroslag remelting process adopts the same technical scheme as the embodiment 1, and the forging process adopts the following technical scheme:

forging: forging in a specific forging mode, wherein the forging mode comprises soaking treatment and forging, the forging mode comprises upsetting and radial forging, and the specific forging mode comprises the following steps: the pass deformation is 50%, the pass reduction is 120mm, the pass heating temperature is 1170 ℃, and the pass deformation mode is square-ellipse-circle. In particular, the amount of the solvent to be used,

soaking treatment: soaking the air-cooled 2.5-ton (phi 510mm) steel ingot under the soaking conditions: firstly heating the mixture to 1170 ℃ at the heating rate of 2.3 ℃/min, and preserving the heat for 4 h.

Upsetting and drawing and diameter forging: the steel ingot after soaking treatment is sent into a press of 4500t for upsetting and drawing for the first time for 8min, the finish forging temperature is 850 ℃, the diameter is 530mm, the reduction is 120mm, and the deformation mode is 530mm square-phi 535mm ellipse-phi 530mm circle; then the blank is heated in a furnace again and heated at 1170 ℃ for 90min, and then the blank is sent into a press of 4500t for second upsetting and drawing for 10min, the final forging temperature is 750 ℃, the diameter is 450mm, the reduction is 120mm, and the deformation mode is 440mm square billet-phi 455mm ellipse-phi 450mm circle; then heating the mixture in a furnace again at 1170 ℃ for 90min, and then sending the mixture into a press of 4500t for primary drawing for 15min until the diameter is 300mm, the reduction is 120mm, the deformation is 55%, and the deformation mode is 310mm square billet-phi 305mm ellipse-phi 300mm circle; and then the steel is heated in a furnace again at 1170 ℃ for 90min, then the steel is forged for 20min in a 1600t diameter forging machine for one fire time, the final forging temperature is 850 ℃, the diameter after forging is 200mm, then the steel is air-cooled to room temperature to obtain a 00Cr19Ni10N steel bar with the diameter of 200mm, the tensile strength at the high temperature of 350 ℃, the yield strength at the high temperature of 350 ℃, the tensile strength at the room temperature and the yield strength at the room temperature can not meet the requirements of the RCCMM3306 standard, and the high-power and low-power tissues are not uniform, which is shown in Table 9 and Table 10.

TABLE 9 Properties and structures of low-carbon nitrogen-containing austenitic stainless steel bars prepared in comparative example 2

TABLE 10 chemical composition (wt%) of the low carbon nitrogen austenitic stainless steel bar prepared in comparative example 2

Comparative example 3

The comparative example provides a manufacturing method of a low-carbon high-strength nitrogen-containing austenitic stainless steel bar produced by adopting a conventional chemical component control range, which sequentially comprises the following working procedures: smelting, electroslag remelting and forging. Except that the following technical scheme is adopted in the material preparation step in the smelting process, the technical scheme in the embodiment 1 is adopted in other steps of the smelting process, electroslag remelting and forging processes. In particular, the amount of the solvent to be used,

a smelting process:

(1) preparing materials: the method comprises the following steps of mixing low-carbon ferrochrome, metallic nickel, electrolytic manganese, ferrosilicon, ferrochrome nitride and scrap steel, and preparing a steel ingot containing C: 0.026%, Si: 0.54%, Mn: 1.45%, S: less than or equal to 0.002%, P: less than or equal to 0.017 percent, Cr: 18.8%, Ni: 9.3%, Cu: less than or equal to 1.00 percent, Co: less than or equal to 0.06 percent, N: 0.05%, B: less than or equal to 0.0018 percent, Nb + Ta: batching in a mode of less than or equal to 0.15 percent, wherein 1/3 weight parts of the low-carbon ferrochrome and the nitriding ferrochrome are reserved respectively.

The above ingredients are adopted for smelting, electroslag remelting and forging, the diameter is 200mm after final forging, then the air cooling is carried out to the room temperature, the 00Cr19Ni10N steel bar with the diameter of 200mm is obtained, and the tensile strength at the high temperature of 350 ℃, the yield strength at the high temperature of 350 ℃, the tensile strength at the room temperature and the yield strength at the room temperature can not meet the requirements of the RCCMM3306 standard, and are specifically shown in tables 11 and 12.

TABLE 11 Performance and Structure of Low-carbon Nitrogen-containing Austenitic stainless Steel rod prepared in comparative example 3

TABLE 12 chemical composition (wt%) of the low carbon nitrogen austenitic stainless steel bar prepared in comparative example 3

C	Si	Mn	P	S	Cr	Ni	N	Nb+Ta	Co	Cu	B
												0.026	0.54	1.45	0.017	0.002	18.8	9.3	0.05	0.008	0.03	0.2	0.0009

In conclusion, by adopting the technical scheme of the invention, the low-carbon high-strength nitrogen-containing austenitic stainless steel with uniformly distributed chemical components and tissues, high purity and high strength can be obtained.

Claims

1. The manufacturing method of the low-carbon nitrogen-containing austenitic stainless steel bar is characterized by sequentially comprising the following steps of: smelting, electroslag remelting and forging; in the electroslag remelting process, the steel ingot obtained in the smelting process is used as an electrode bar of an electroslag furnace, and remelting and crystallization are carried out by using specific slag; in the forging procedure, the crystallized steel ingot is forged into a material in a specific forging mode;

the specific forging modes comprise upsetting and radial forging, wherein the upsetting comprises the following steps: the pass deformation is less than 35%, the pass reduction is 50-80 mm, the pass heating temperature is 1130-1150 ℃, and the pass deformation mode is as follows: ellipse-circle.

2. The method of manufacturing a low carbon, nitrogen-containing austenitic stainless steel rod according to claim 1,

according to the weight percentage content, the CaF₂、Al₂O₃CaO and MgO are sequentially (65-68%), (18-20%), (5-10%), (3-5%), preferably CaF₂、Al₂O₃CaO and MgO are 65%, 20%, 10% and 5% in sequence.

3. The method of manufacturing a low carbon, nitrogen-containing austenitic stainless steel rod according to claim 1 or 2,

in the smelting procedure, the steelmaking raw materials are mixed in a mode that the steel ingot obtained after smelting or the stainless steel bar obtained finally has specific components, and the specific components comprise the following components in percentage by weight: c: 0.020 to 0.030%, Si: 0.3-0.6%, Mn: 1.3-1.8%, S: less than or equal to 0.002%, P: less than or equal to 0.015 percent, Cr: 19.20 to 19.70%, Ni: 9.20-9.80%, Cu: less than or equal to 1.00 percent, Co: less than or equal to 0.06 percent, N: 0.065-0.075%, B: less than or equal to 0.0018 percent, Nb + Ta: less than or equal to 0.15 percent;

4. The method of manufacturing a low carbon, nitrogen-containing austenitic stainless steel rod according to any of claims 1 to 3,

the smelting process sequentially comprises melting treatment, refining treatment, vacuum degassing treatment and casting molding; the steelmaking raw materials comprise low-carbon ferrochrome, metallic nickel, electrolytic manganese, ferrosilicon, ferrochrome nitride and scrap steel.

5. The method of manufacturing a low carbon, nitrogen-containing austenitic stainless steel rod according to any of claims 1 to 4,

before the electroslag remelting process, the steel ingot obtained in the smelting process is subjected to cutting treatment and surface polishing treatment, and then is used as an electrode bar for electroslag remelting.

6. The method of manufacturing a low carbon, nitrogen-containing austenitic stainless steel rod according to claim 1 or 5,

in the electroslag remelting procedure, the electroslag remelting current is 11-13 KA;

preferably, in the electroslag remelting process, 1 to 10 wt%, preferably 1 to 8 wt% of the electrode rod is used for feeding the crystallized steel ingot;

preferably, the steel ingot obtained by electroslag remelting is demoulded and cooled to room temperature to obtain the low-carbon nitrogen-containing austenitic stainless steel blank.

7. The method of manufacturing a low carbon, nitrogen-containing austenitic stainless steel rod according to claim 1 or 6,

in the forging process, soaking treatment is carried out on a low-carbon nitrogen-containing austenitic stainless steel blank obtained by electroslag remelting before upsetting and drawing, wherein the soaking treatment comprises the steps of heating to 1130-1150 ℃ at a heating speed of 1-10 ℃/min, and then preserving heat for 3-5 hours at the temperature.

8. The method for manufacturing a low-carbon austenitic stainless steel rod containing nitrogen according to claim 1 or 7, wherein the condition of upsetting in the forging step includes: upsetting and drawing are carried out by adopting the specific forging mode, wherein the starting forging temperature is more than or equal to 1000 ℃, the final forging temperature is more than or equal to 800 ℃, and the upsetting and drawing times are 1-3 times, preferably 2-3 times; the upsetting and drawing time is 5-20 min each time;

preferably, in the forging step, the upsetting condition includes: upsetting and drawing by adopting the specific forging mode, wherein the starting forging temperature is 1050-1100 ℃, the final forging temperature is 800-900 ℃, and preferably, the upsetting and drawing time is 5-15 min each time;

preferably, in the upsetting in the forging step, the specific forging method includes: the pass deformation is 30-32%, the pass reduction is 65-75 mm, the pass heating temperature is 1130-1150 ℃, and the pass deformation mode is as follows: ellipse-circle;

preferably, in the upsetting in the forging step, the specific forging method includes: the pass deformation is 31 percent, the pass reduction is 70mm, the pass heating temperature is 1140 ℃, and the pass deformation mode is as follows: ellipse-circle;

preferably, in the upsetting in the forging process, upsetting is carried out twice in a 4500t press, and the second upsetting deformation is larger than the first deformation;

preferably, in the upsetting in the forging process, each time upsetting is finished, the forging process returns to the furnace for reburning to reach the forging temperature required by the next upsetting, and preferably, the conditions of returning to the furnace for reburning and heating after each upsetting are as follows: the temperature is 1130-1150 ℃ and the time is 90-120 min.

9. The method of manufacturing a low carbon, nitrogen-containing austenitic stainless steel rod according to any of claims 1, 7 and 8,

in the forging process, radial forging is carried out after upsetting and drawing are finished; the radial forging conditions include: the open forging temperature is 1000-1140 ℃, the finish forging temperature is 800-900 ℃, and the time is 5-20 min;

preferably, the conditions of the radial forging include: the start forging temperature is 1000-1100 ℃, the finish forging temperature is 800-900 ℃, and the time is 10-20 min;

preferably, the radial forging is carried out on a 1600t radial forging machine, one-time forging forming is carried out, and the radial forged steel is cooled in air to obtain the low-carbon nitrogen-containing austenitic stainless steel rod.

10. The method of manufacturing a low carbon, nitrogen-containing austenitic stainless steel rod according to any of claims 1 to 9,

the low-carbon nitrogen-containing austenitic stainless steel bar with the diameter of more than 200mm can be prepared by adopting the manufacturing method; preferably, the tensile strength at high temperature of 350 ℃ of the low-carbon nitrogen-containing austenitic stainless steel bar is more than or equal to 410MPa, the yield strength at high temperature of 350 ℃ is more than or equal to 140MPa, the tensile strength at room temperature is more than or equal to 560MPa, and the yield strength at room temperature is more than or equal to 260 MPa.